Spinnerets



i 19.67 D. J. WOOD ETAL 3,321,802

SPINNERETS Filed March 26, 1965 United States Patent C) 3,321,802 SPINNERETS Derek 1. Wood, Raglan, William G. larr, Ahergavenny, and Faster C. C. Sanders, Cwmhran, England, assignors to British Nylon Spinners Limited, Pontypool, Monmonthshire, England Filed Mar. 26, 1965, Ser. No. 442,857 Claims priority, application Great Britain, Mar. 31, 1964, 13,327/64 18 Claims. (Cl. 18-8) This invention relates to improvements in spinnerets used in the manufacture of filaments having a non-circular cross-section and is particularly directed to spinnerets employed in the manufacture of filaments having a multilobal cross-section.

Spinnerets for the manufacture of filaments having a non-circular cross-section contain orifices which frequently take the form of at least one arm and more usually three or more such arms, each of the said arms interconnecting with at least one other arm. As examples of such orifices we have those which take the form of thin rectangular slots for the production of elliptical crosssection filaments, Y-shaped orifices for the production of trilobular and the like cross-section filaments, cruciform-shaped orifices for the production of tetralobular and the like cross-section filaments and orifices in the form of a hollow E for the production of essentially crescent-shaped filaments. A feature common to the aforementioned and related types of orifices is that they all have at least two extended tips.

In the spinning of artificial fibres through orifices comprising, for example, a plurality of equi-length arms in terconnecting at a single point, i.e. the centre point of the orifice, there is a marked tendency for the filaments, which initially appear having substantially the same shape as the spinneret orifice, to assume a circular cross-section. This is especially true of melt spun polymers.

To reduce this tendency it has been proposed to change the shape of the tip portions of the orifices to allow more polymer to flow therethrough. Examples of such changes in shape are given in US. patent specification No. 2,945,- 739, in which the arms of the orifice have abruptly expended tips and in US. patent specification No. 3,109,195 in which the tips of the arms are traversed by intersecting slots.

We have now found that the spinning material can be preferentially supplied to the tips of the orifice arms without changing the shape of the extrusion orifice by the provision of one or more counterbores extending transversely of the tips of the said arms. The counterbores may be arranged either to supply a greater volume of spinning material to the tips of the arms relatively to the centre portion, or as the only means for supplying the spinning material to the orifices.

According to the present invention therefore there is provided a spinneret for the manufacture of artificial filaments having a non-circular cross-section comprising a spinneret plate having a front and back face and containing therein an extrusion orifice consisting of at least two interconnecting slot-like arms there being provided at least one bore communicating with the tip portions of the slot-like arms of the extrusion orifice, which bore is formed in the back face of the plate and extends towards, but does not reach, the front face thereof.

Normally the extrusion orifices will extend through the spinneret plate from the back face, or from a counterbore formed therein, to the front face. However, the invention also includes the case where the orifice extends from the front face of the spinneret plate to some point within the plate and communicates with the back face,

3 ,32 l Patented May 3Q, 1967 or with a counterbore formed therein, only through the aforementioned bore or bores.

Preferably the bore, or bores, will have a depth equal to at least half the capilliary depth of the arms of the extrusion orifice.

The term bore as used in this specification includes channels which communicate with the tip portions of two or more arms of an extrusion orifice. Thus the term includes a straight channel between the tip portions of the extending arms of a hollow E orifice, a roughly semicircular channel connecting the tip portions of the arms of a T-shaped orifice having three arms of equal length, and a circular channel connecting the tip portions of, for example, a Y-shaped orifice.

The front face of the spinneret is that portion through which the spinning material is extruded in filament form and the back face of the spinneret is that portion through which the spinning material is introduced to the extrusion orifice. The capillary depth of the arms of an orifice is the depth to which the arms extend from the front face of the spinneret towards the back face thereof.

The invention will now be illustrated by reference to the accompanying drawings.

In the drawings:

FIGURES 1 through 6 show, diagrammatically, plan views and cross-sectional fragments of three embodiments of one aspect of the invention;

FIGURES 7 and 8 show, diagrammatically, a plan view and a crosssection of a fragment of one embodiment of another aspect of this invention.

In FIGURES 1 through 3 represent fragments of plan views of the back faces of spinnerets containing Y-shaped orifices and FIGURES 4 through 6 cross-sections of the fragments taken along the line A-A.

The Y-shaped extrusion orifice comprises three uniform equi-length arms 1 radiating symmetrically from a central point 2. The orifice extends fromthe front face 3 of the spinneret to communicate with a counter bore 4 which is formed in the back face 5 of the spinneret. In FIGURES l and 6 an annular bore 6 is formed within the counter bore 4 and extends from the circumference thereof to a point along the length of the arms 1 of the orifice thus reducing the capillary depth of the arms 1 at their tips and leaving a plateau between each of the arms of the orifice. In FIGURES 2 and 5 an annular bore 8 is formed within the counter bore 4 and extends from the circumference thereof to the tips of the arms 1 thus reducing the effective capillary depth of the arms 1 at their extreme tips. The plateau 9 which is thereby formed between each-of the arms of the orifice is chamfered to allow a smooth flow of the spinning material towards the outermost side of the annular bore 8. In FIG- URES 3 and 6 bores 10 having diameters greater than the width of arms 1 are formed at tips of arms 1 to reduce the capillary depth of the arms at those points. These bores may, of course, be formed as extensions to the tips of the arms provided that they retain communication therewith.

In use in, for example, a melt spinning operation, molten polymer flows from the top face 5 of the spinneret into the counter bore 4 and thence into the arms 1 of the extrusion orifice and is extruded into a filament. The effect of the bores 6, d and 10 which, as aforesaid, reduce the capillary depth of arms l at their tip regions, is to provide a greater flow of polymer to the extrusion orifice at these points. The filament which is thus extruded will, immediately after extrusion, have a substantially trilobular cross-section but with slightly bulbous tips to the lobes. Subsequent attenuation of the filament before solidification draws away the excess polymer from the lobe tip regions in contrast to the usual procedure in which the tip regions themselves are drawn in towards the centre of the filament, thus the tendency for the filament to assume a circular cross-section is reduced.

FIGURE 7 represents a fragment of a plan view of the back face of a spinneret containing a Y-shaped extrusion orifice and 2a is a cross-section of the fragment taken along the line B-B.

As in FIGURES 1 through 6, the Y-shaped extrusion orifice comprises three uniform equi-length arms 11 radiating from a central point 12. The orifice extends from the front face 13 of the spinneret to some point within the spinneret plate. A counter bore 14 is formed in the back face 15 of the spinneret plate and coaxially with the extrusion orifice but does not extend sufficiently far into the spinneret to communicate with it. Bores 16 are formed in the base of the counter bore 14 to communicate with tips of the arms 11 and to reduce the capillary depth of the arms at these points.

In this embodiment the molten polymer flows into the counter bore 14 and thence through the bores 16 into the tips of the arms 11 filling up the remainder of the orifices as it flows therethrough. A filament is thus produced having a substantially trilobular cross-section but with a slight excess of polymer at the lobe tips, which excess is drawn away during the attenuation Which takes place prior to solidification, thus reducing the tendency of the lobe tips to be drawn into centre of the filament.

It will be obvious to those skilled in the art that the bores 16 may be joined together to form a single annular bore of the type designated 6 in FIGURES 1 and 4, or that they may be formed as extensions to the tips of the arms 11 provided they retain communication therewith. An annular bore of the types designated 8 in FIGURES 2 and may also be employed.

For convenience the orifices of this invention may be referred to as tip feed" orifices.

The following examples illustrate the invention but are in no way intended to be limitative thereof.

Example 1 A spinneret for use in the melt spinning of polyamides into a filament having an essentially trilobal cross-section contains an orifice of the type described with reference to FIGURES 3 and 6. In this spinneret the counterbore 4 has a diameter of 0.130" and is formed in the back face 5 of the spinneret to extend to within 0.020" of the front face 3 of the said spinneret. An orifice having three arms 1, each 0.020" long and 0.004" wide and at an angle of 120 to each other, is formed in the front face 3 of the said spinneret and extends towards the back face thereof to communicate with the counter bore 4 as shown. Three circular bores of 0.012" diameter and having their centres 0.005" from tips of the arms 1 and 0.015" from the centre of the orifice are formed in the bottom of the counter bore 4 and extend to within 0.010 of the front face 3 of the spinneret. The capillary length of the orifice arms 1, 0.020", is thus reduced to 0.010" for a distance of 0.011" from the tips. The effect of these bores 10 is to allow a greater flow of polymer to be supplied to the tip areas of the arms of the orifice.

Example 2 A spinneret plate containing 6 extrusion orifices identical with the one described in Example 1, in which the orifices were formed in the base of a straight channel across the plate and having, in addition, cross-channels to ensure uniform flow of molten polymer to the orifices, was used in cooperation with a normal melt spinning apparatus to produce a yarn having filaments of trilobal cross-section from polyhexamethylene adipamide polymer. The polymer had a relative viscosity of 43.5 and was spun, using a spinneret temperature of 270 G, into a 9 d.p.f. yarn at a spinning speed of 3930 ft./min.

This yarn was compared with a similar yarn spun under identical conditions using a spinneret plate in which the Orifice: Modification ratio Standard 2.40 Tip feed 2.89

It is clear from the above table that the tip feed orifices gave filaments having a more well defined trilobal shape than the standard orifices. This improvement in shape Was not affected by subsequent drawing, the modification ratio remaining substantially unaltered.

Example 3 A spinneret plate similar to that employed in Example 2 except that the capillary length of the tips of the arms of the orifices was reduced to 0.005 by the provision of longer bores (10 in FIGURES 3 and 6), was used to spin, under the same conditions as described in Example 2, filaments haivng a trilobal cross-section from the polymer of Example 2. The modification ratio of the undrawn filaments in this case was 2.63 compared with 2.40 for filaments spun through standard orifices.

Example 4 A second spinneret for use in the melt spinning of polyamides into a filament having an essentially trilobular cross-section contains an orifice of the type described with reference to FIGURES 7 and 8. In the spinneret the counter bore 14 is formed in the back face 15 of the spinneret plate to extend to within 0.030 of the front face 13. An orifice having the same dimensions as that described in Example 1 is formed in the front face 13 of the spinneret coaxially with the bore 13 and extends to within 0.040", of the back face thereof, i.e. to within 0.010" of the counter bore 14. Three circular bores 16 of 0.012" diameter are formed in the bottom of the counter bore 14 such that their axes are on a line passing through the arms 11 of the orifice at points 0.005 from the tips 0.015 from the centre of the orifice, and extend to within 0.010 of the front face of the spinneret thus intersecting the tips of the arms 11 of the orifice and reducing the capillary length of the orifice from 0.02 0" to 0.010" for a distance of 0.011" along the arms thereof. The bores 16 thus provide the polymer supply means to the orifice from the counter bore and to allow a greater flow of polymer to the tip areas of the orifice, thus allowing the production of better shaped filaments than can be obtained using conventional orifices.

What we claim is:

1. A spinneret for use in spinning artificial filaments having non-circular cross-sections comprising a spinneret plate having a front and back face and containing therein an extrusion orifice consisting of at least two interconnecting slot-like arms having tip portions, said tip portions of said slot-like arms having at least one bore communicating with said tip portions of said extrusion orifice, said bore being of such depth as to avoid reaching said front face of said spinneret.

2. The spinneret according to claim 1 wherein the bore communicating said tip portions of said extrusion orifice is a counter bore of a bore in the back face of said spin neret plate.

3. A spinneret according to claim 2, wherein the depth of the bore communicating with all of said tip portions of said extrusion orifice is at least one half the depth of said extrusion orifice.

4. The spinneret according to claim 2 wherein individual circular counter bores are provided at the tip portions of each arm of the extrusion orifice having diameters greater than the width of said arms but not extending beyond the bore in the back face of said spinneret plate.

5. The spinneret according to claim 2 wherein individual circular counter bores are provided at the tip portions of each arm of the extrusion orifice having diameters greater than the Width of said arms.

6. A spinneret according to claim 2 wherein the extrusion orifice comprises three or more slot-like arms radiating from a point, the tip portions of the said arms being circumscribed by a counter bore having an annular shape.

7. A spinneret according to claim 6 wherein the extrusion orifice consists of three arms of substantially equal length set apart at angles of 120.

8. A spinneret according to claim 6 wherein the bore having an annular shape encompasses part of the tip portions of the said arms.

9. A spinneret according to claim 8 wherein the extrusion orifice consists of three arms of substantially equal length set apart at angles of 120.

10. A spinneret according to claim 1 wherein the extrusion orifice is formed in the front face of the spinneret plate and extends towards the back face thereof, not reaching said back face but communicates therewith through the said bore.

11. A spinneret according to claim 10 wherein the spinneret plate contains a counter bore in the back face thereof, which counter bore does not extend through the plate to communicate with the extrusion orifice.

12. A spinneret according to claim 10 wherein the depth of the bore communicating with the tip portions of the arms of the extrusion orifice is at least half the extrusion orifice depth thereof.

13. A spinneret according to claim 10 wherein circular bores are provided at the tip portions of each arm of the extrusion orifice having diameters greater than the width of said arms and with their axis beyond the said tip portions thereof.

14. A spinneret according to claim 10 wherein circular bores are provided at the tip portions of each arm of the extrusion orifice having diameters greater than the Width of the said arms, each bore having its axis passing through a point on an arm at a distance from the tip thereof equal to the radius of the said bore.

15. A spinneret according to claim 10 wherein the extrusion orifice comprises three or more slot-like arms radiating from a point, the tip portions of the said arms being circumscribed by an annular bore.

16. A spinneret according to claim 15 wherein the extrusion orifice consists of three arms of substantially equal length set apart at angles of 17. A spinneret according to claim 15 wherein the annular bore encompasses part of the tip portions of the said arms.

13. A spinneret according to claim 17 wherein the extrusion orifice consists of three arms of substantially equal length set apart at angles of 120.

References Cited UNITED STATES PATENTS 3,006,026 10/1961 Martin et a1 18-8 3,041,894 7/ 1962 Cupler. 3,109,195 11/1963 Combs et a1. 188 3,174,364 3/1965 Sims 18-8 X 3,230,582 1/1966 Hoffman et a1. 18-8 X FOREIGN PATENTS 865,843 4/ 1961 Great Britain.

WILLIAM J. STEPHENSON, Primary Examiner, 

1. A SPINNERET FOR USE IN SPINNING ARTIFICIAL FILAMENTS HAVING NON-CIRCULAR CROSS-SECTIONS COMPRISING A SPINNERET PLATE HAVING A FRONT AND BACK FACE AND CONTAINING THEREIN AN EXTRUSION ORIFICE CONSISTING OF AT LEAST TWO INTERCONNECTING SLOT-LIKE ARMS HAVING TIP PORTIONS, SAID TIP PORTIONS OF SAID SLOT-LIKE ARMS HAVING AT LEAST ONE BORE COMMUNICATING WITH SAID TIP PORTIONS OF SAID EXTRUSION ORIFICE, SAID BORE BEING OF SUCH DEPTH AS TO AVOID REACHING SAID FRONT FACE OF SAID SPINNERET. 